Apparatus for interiorly coating lamps, tubes, and the like



0. H. BIIGGS May 30, 1939,

APPARATUS FOR INTERIORLY COATING LAMPS, TUBES, AND THE LIKE Original Filed July 20, 1932 -1--- #:iti

L L rFIIIIlII .Il

for

ll my invention. I

Patented May 30, 1939 I umrsp sTATss PATIENT OFFICE APPARATUS FOR INTERIORLY' COATIN LAIMPS, TUBES, AND THE LIKE Orrick H. Bles B verly, MassL, assignor to Bygrade Sylvania Corporation, Salem, Man, a corporation of Massachusetts Original application July 20, 1932, Serial No. 623,504. Divided and this application December 31, 1927, Serial No. 182,735

7 Claims.

This invention relates to evacuated or gas-filled vessels, and with particularity to an apparatus for providing such vessels with light-reflecting internal coatings.

In certain of the arts, for example in the incandescent lamp art, it is desirable to provide the lamp with an integral reflector, and for this purpose it has been proposed to cover the outside surface of the lamp with a coating of silver, or even 10 to provide the lamp with a tight-fitting cap. 6

These latter expedients, however, have certain disadvantageswhich will become apparent from the following descriptions. I have found that a reflecting layer of a specially chosen material covering the inside surface of the lamp bulb is in many respects superior to the prior art reflectors. It is one of the objects of the present invention to provide a vessel, for example the glass bulb of an incandescent lamp, with a firmly adherent and smooth internal coating having a high specular reflection characteristic, which coating is sub stantially free from contamination during the life of the lamp.

Another object is to provide an improved apparatus for interiorly coating a vessel witha lightreflecting. material confined to a pre-determined localized area. on the inner surface of the vessel.

Another object is to provide improved means for evaporating metal, as for example aluminum,

within a vessel in order to coat its inside or a well defined part thereof, with a firmly adherent and light-reflecting layer of the metal, and to provide operating conditions for this process which permit its practice in the most satisfactory manner. i

In certain types ,orlamps for example, those having a relativelylong and constricted neck I portion and a spherical or bulb portion, ordinary coating methods are inapplicable to restrict the coating to a section only of the bulb, particularly if the coating isto be deposited by an evaporation process.

Accordingly, a principal object is to provide a stencil or shield which may be conveniently in- 45 serted into, and removed irom, a vesselhaving a comparatively narrowneck.

Theseand other objects and advantages of the present inventionwill be apparent from the following descriptions of specific embodiments of my new method, and of the article of manufacture obtained therewith, with reference to the drawing in which:

l 'iguijls a side elevatlonal view, partly in section, of an incandescent lamp made according to Fig. 2 is a side' elevational view of a lamp bulb, with the neck of the bulb in section, showing how the shield used according to my invention is introduced into the bulb. 4 Fig. 3 shows a device for treating a bulb according to my invention, with the upper portion of the bulb sectioned, in order to reveal the shield and ribbon filament in operative position.

Fig. 4 is a detail view of the ribbon filament. Fig. 5 is a plan view oia device for finishing acoated bulb, with a bulb in, position; and Fig. 6 is a plan view of an alternative device for finishing bulbs Referring to Fig. 1, numeral i denotes the glass bulb, 2 the filament, and 3 the base of an incandescent lamp of any desirable shape, design, cola, or other characteristics. The inside of the glass-bulb .l is covered with a firmly adherent thin and smooth coating 4 bf light reflecting material, as for example silver or aluminum. Lamps of this type are especially suitable for use in lamp flxtures providing indirect illumination; and, ac cordingly, Fig. 1 shows the reflecting layer as approximately covering the semispherical portion opposite the stem 01' a spherical lamp. It is, however, understood that any portion of any configuration, of the inside of a lamp of any desired shape or of any vessel generally, may be coated according to my invention.

' It is' apparent that lamps of this typehave th important advantage that the reflecting layer is perfectly protected against any mechanical injury, oragainst vapors etc., to which exterior coatings are exposed. Fln'then'the rough'surface of exterior coveringsheretoiore employed, becomes easily covered with dust, soot, etc., which being diflicultto remove without injuring the reflector. not only spoils the appearance of the lamp, but also renders the installation less eiilcient due to the presence of an energy absorbing black body 40 near the path of the reflected light. Still another .importantadvantage of the inside coating is the fact th'atit remains exceptimally cool during operation of the lamp, even cooler than an uncoated lamp 01' similar rating. This is dueto the circumstance that the radiant energy passes through theglass walls once in the case of an 'ordinarybulb andtwlceinthecaseoianexternal reflector, whereas my new lamp reflectsthe rays without permitting them to penetrate the B1888 at the reflectonsothatitremainscool totheestent for examplethat a W and exposed, inside coated 800 watt lamp handled with Althonghtbcinternaieoaflngmayccn|istct easily, probably due to the copper contents of commercial silver, which is the only silver prac-' tical for purposes of this kind. I have also found that the color, and therefore the light reflecting characteristics of aluminum, are preferable to those of other metals.

My new process of internally coating bulbs, or vessels generally, of the above described nature, is preferably carried out with the aid of a device shown in Figs. 2, 3, 4. This device is supported by a casting l having a body H and two extensions l2 and I4, which may be suitably mounted upon a working table by means of an insulated clamp or similar conventional means not herein shown. The body ll. of casting l0 has terminal l5 of an electric lead I6 screwedthereto, and the upper extension I2 is provided with a conical rubber washer IS. A shield structure 2|! comprises a sleeve 2| having an extension 22 at its lower end and a substantially conical collapsible shield 23 fastened to its upper end. The shield consists of leaves 24 which may be made of any suitable material, as for example thinsheet metal. The leaves overlap to make the shield tight, and at its apex the shield cone is so fastened to sleeve 2| that the leaves can be contracted, as shown in Fig. 2, permitting the bulb to be slipped over it. The shield being completely inserted, its leaves spread apart so that the approximately circular upper edge of the shield rests against the inside of the bulb wall. The lower extension 22 of shield sleeve 2| fits into extension l2 of casting I0, forming a joint as shown in Fig. 3.

The lower extension H of casting I0 is connected to port 3| of an exhaust pump manifold by means of a tube or hose 32. Conduit 34 with cook 31 leads to an exhaust pump, and open conduit 35 with cook 36 connects the manifold with the atmosphere. i

A ribbon filament 40, preferably made of tungsten, with a bowl shaped recess 4|, is screwed to leads 42 and '43. Lead 42 is fastened to casting II at 44 and therefore in electrical connection with conductor l6. Lead 43 has an insulating covering 45, for exanfple of glass, and extends downwardly through casting l0 and'tube 32. into extension 39 of the, pump fixture, and is fastened to seal 46, which is tightly joinedto 30 by means of a rubber tube 41. 7 Terminal 48 of conductor 49 is screwed to' seal 46 and therefore in electrical connection with the second 'lead of -the ribbon filament. Y

The manner of using my device is as follows: A lamp bulb or other vessel is first carefully cleaned and dried in order to remove any dust or 'dirt.which might mechanically impair the coating, and alsoin order to eliminate any harmful substances, as alkalies, which are especially harmful to aluminum films. The metal to be evaporated, as for instance aluminum, is placed on thefllament in the formof pellets or small shavings, and the bulb is then slipped over the shield structure, as above described, and pressed against the rubber washer where a vacuum tight joint is established during the following evacuation process. Fig.3'.shows the bulb in this position. The pumps are then started and the bulb exhausted below the glow point, that is, to a vacuum of approximately to 30 microns. During the exhaust period the bulb is heated, for example by means of an open flame, in order to drive out any occluded gases. During this step of the process the temperature of the bulb is approximately 300 degrees centigrade. When the bulb has cooled slightly, the metal is quickly evaporated by heating the tungsten filament. The filament is heated byapplying a sufficiently strong E. M. F. across the leads l6 and 49. I have found that the reflecting film on the inside of the bulb is of superior quality if the evaporating process takes place fairly quickly, forexample in approximately five seconds. The hot filament radiates considerable energy, and if maintained at a high temperature for a longer time, other parts of the enclosure might be also heated and release contaminating gases. The metal vapors condense quickly upon the surface of the bulb where it is not protected by the shield, but air should not be admitted until the filament has cooled down, in order to prevent oxidation.

Although the edge of the coating is comparatively well defined, especially if the shield is carefully made and inserted, it is often desirable to remove excess metal in order to straighten the zigzag line which may have been left by the 11'- regular edge of the shield. This finishing step is preferably performed with the aid of a small high speed builing wheelinserted in the bulb by means of an'arrangement shown in Fig. 5. In this figure, 5| is a working table with a motor support 52, fulcrumed at 50, and bulb supporting means mounted thereon. The bulb supporting,

means comprises a lamp holder 54 with a base 55 and resilient arms 56, and a bulb guide 51 with arms 58 having rollers 59 rotatably mounted upon the ends thereof. Base 55is mounted on a driving gear journalled at 62 and rotated with suitable speed by any means adapted for this purpose, as for example a worm gear within housing 65 driven by motor 66. The motor 10 has a base 1| sliding upon rails 12 and rotating with support 52 around fulcrum 50. The motor III has a shaft 8| with a buffer wheel mounted thereon.

As indicated in Fig. 5, the bulb can be easily and quickly fastened in the rotating holder, the shaft 8| can be inserted in the bulb, and the edge of the coating straightened by means of the buffer wheel, which may be conveniently positioned and directed as will be apparent from Fig. 5 and the above description, without further detailed explanation.

This method of finishing a bulb is quite satisfactory in the case of comparatively thin metal coatings, whereas for thicker flhns I found that an alternative method is preferable, the arrangement for this method being schematically shown in Fig. 6. In this figure, 92 is a felt disc impregnated with an abrasive, of about the diameter of the largest section of the bulb, and mounted on a spindle 9| which can be rotated at high speed, preferably about 3500 R. P. M., by means of any suitable drive. Fig. 6 indicates for this purpose a gear box 90 with driving shaft 95. The spindle 9| is long enough to permit insertion of the softfelt disc, which, upon being rotated at high speed, flattens out into a rather hard and stiff structure. The periphery of the disc approximately coincides with the coating edge to be cleaned, and is therefore in constant contact c ture shield for insertion in such tubes while 7 therewith, so that the entire availableabra'sive surface is always active, whichwassuresspeedy I and certain action. I

It should be understood that. the present disclosure is for the purpose of illustration only, and

thatthis invention includes all modifications and equivalents which fall within the scope of;the

appended claims. I .f I

This application is a division. of application Serial No. 623,504, flied July 20, 1932, and application Serial No. 691,322, filed September 28, 1933. Continuations-in-part of'thesaid applications have been filed on December 7, 1936, as application serial Number 114,562, and on November 2, 1937, as application Serial No. 172,397

and a continuation-in-part application Serial No.

183,063, flied January 3, 1938.

What I claim is: I 1. An apparatus for coating the interior surfaces of tubes with metal comprising in combiinsertion, in such tube and for expansion therein to shield the surfaces of the tube desired to be left uncoated.

3. An apparatus for depositing vaporized metal upon limited areas of the interior surfaces of tubes comprising an expansible and contractiblein collapsed condition and cxpansible to shield the'remaining areas from metalvapor. 1

4. In an apparatus for forming a layer of metal upon limited areas of the interior surface of tubes, a shield for the remaining areas comprising a central web and a series of relatively movable overlapping resilient segments integrally an- 1 chored to said web and disposed at equal angles thereto. I I

5. A shield comprising a circular web portion,

and a series of-resilient strips integral therewith and bent at an angle thereto to form an expansible and contractible frustro-conical cup-like shield. I I I 6. man apparatus for forming a coating upon a localized area on. the interior of a bulb having a restricted neck portion, a shield for the said area said shield comprising a series of relatively movable overlapping resilient segments fastened to an annular hub and normally'disposed at equal angles thereto. I

7. An apparatus for controlling the application of a vaporized coating material to a local-e izedarea on the interior of a bulb comprising 25 a member having an annular hub portion, a series of resilient strips carried by said hub and bent at an angle thereto. to form an expansible and contractible trusto-conical cup-like shield,

a lead-in wire extending through said annular hub and insulated therefrom, means to support the material to be vaporized above said hub. a connection from said lead-in wire to one point on said support and another connection to another point on saidsupport, and means topass current through said lead-in wire and said other connection to heat said support and vaporize said material on to said localized area.

' ORRICK H. BIGGS. 

